MICROWAVE DEMULSIFICATION

The laboratory and field tests have demonstrated that microwave radiation can break oil-water-solid emulsions, and recover oil from oily sludge and bottoms sediment and water (BS&W). As a result, this innovative microwave technology provides a new option in the minimization of waste and resource recovery in petroleum industry. Test samples include crude oil-water emulsions and waste sludge from a gas compressor station.

Separations of oil from water by the gravity sedimentation, conventional heating and microwave radiation are compared. There are cases that microwave radiation shows faster separation than that by other two conventional methods.     

Electrostatic enhancement of coalescence of water droplets in oil: a review of the technology

The technology for electrostatic enhancement of coalescence of water droplets in oil emulsions is critically reviewed. Historically, the electrostatic coalescer was invented for the petroleum-related industries in California [US Patent 987 115 (1911)]. Nowadays, this technology is generally considered for the separation of an aqueous phase dispersed in a dielectric oil phase with a significantly lower dielectric constant than that of the dispersed phase. Various designs have been introduced, with most using alternating current (AC) electric fields with mains frequency (50 or 60 Hz). The direct current (DC) electric field has been less common in the past as compared to the AC. In 1981, the concept of pulsed DC electric fields was introduced, together with insulated electrodes [Trans. IChemE 59 (1981) 229–237; UK Patent 217 1031A (1986)]. Since then, this has become more common in the electrocoalescence technology. Pulsed DC and AC fields are especially useful, when the aqueous phase content of the emulsion is high, to prevent short-circuiting between the pair of electrodes. Processing of oil from old wells is a good example, where the volumetric water content could vary significantly. Reported work by some workers indicates the existence of an optimum frequency, which depends on the electrode coating material, its thickness and the liquid emulsion composition. This is however, a contentious issue which has not been completely resolved. The characteristics and geometry of the electrode system (generally cylindrical or plate) influence the performance of the electrostatic coalescer, and are closely related to the type of the applied electric field and the emulsion used. There are basically two types of electrode: uninsulated electrode and insulated electrode. Combination of electrocoalescence and mechanical separation (e.g., centrifugal force) has also been introduced. Heating and the addition of chemicals have been shown to further enhance the electrocoalescence of water droplets. Other methods that can be combined with the electrical treatment are filtration, methods employing high pressure and temperature, and mixing. This review paper also looks at some of the current specific industrial applications using the electrocoalescence technology. Besides the oil and petroleum industries, this technology has potential applications in the edible oil industries such as palm oil, sunflower oil and vegetable oil processing. Most of the currently available equipment is very big and bulky, having a large inventory of emulsion. Therefore, we see the future trend for new developments to be in the direction of inventing small portable devices, incorporating features such as optimum electric fields and combined electrical and centrifugal forces to further enhance the separation of water-in-oil emulsions. Furthermore, a better understanding of the fundamentals of electrocoalescence will enable a better design of the geometry of the electrodes, of the flow field with respect to the electric fields, the type of dispersion used and the type of the applied electric field.     

Modeling and Optimization of Two Stage AC Electrostatic Desalter

Electrostatic desalters are commonly used to separate water from crude oil emulsions. In this study, a novel mathematical model based on a bivariate population balance equation has been proposed to model the steady state distribution of water droplet sizes and salt concentration along an Alternative Current (AC) electrostatic desalter. Pilot plant data for two heavy crude oils are used to validate the model. Effect of different operational parameters on the outlet dehydration efficiency and salt content of crude oil have been studied. Furthermore, the effect of two-stage desalting on the outlet Basic Sediment and Water (BS&W) and salt content of oil have been studied and the optimized parameters of such configuration have been found by differential evolution method to get the best performance of the electrostatic desalters.     

Preparation of water-in-oil and ethanol-in-oil emulsions by membrane emulsification

In this work, water-in-oil emulsions (W/O) and ethanol-in-oil emulsions (E/O) emulsions were prepared successfully by membrane emulsification. The emulsifiers selected were PGPR and MO-750 for the W/O and E/O emulsions, respectively. For W/O emulsions prepared with an oil pre-filled membrane, the dispersed flux was lower and the droplet size sharper than that obtained with a water pre-filled membrane. On the contrary, for E/O emulsions prepared with the membrane pre-filled with oil, the dispersed phase (ethanol) rapidly pushed out the oil from the membrane pores. Therefore, the pre-treatment of the membrane had almost no effect on the dispersed phase flux and on the droplet size. The droplet size distribution of the E/O emulsion was close to that obtained with a classical homogenizer. The dispersed phase fluxes were high and no fouling was observed for our experimental conditions (1.6 l emulsion, 10 wt% ethanol). These results confirm that membrane emulsification could be an interesting alternative for the preparation of E/O emulsions for the purpose of biodiesel fuels, considering the scale-up ability of membranes and their potentiality for industrial processes.     

Hydrate formation from high water content-crude oil emulsions

Methane hydrate formation and dissociation studies from high water content ( water) - crude oil emulsions were performed. The hydrate and emulsion system was characterized using two particle size analyzers and conductivity measurements. It was observed that hydrate formation and dissociation from water-in-oil (W/O) emulsions destabilized the emulsion, with the final emulsion formulation favoring a water continuous state following re-emulsification. Hence, following dissociation, the W/O emulsion formed a multiple o/W/O emulsion (60 vol% water) or inverted at even higher water cuts, forming an oil-in-water (O/W) emulsion (68 vol% water). In contrast, hydrate formation and dissociation from O/W emulsions ( water) stabilized the O/W emulsion.     

Effect of salt on the structure and properties of sonicated emulsions stabilized by a tertiary oil recovery formulation

Structure of sonicated emulsions obtained by varying sodium chloride concentration in surfactant formulations containing 5% (w/w) TRS 10–410 (a petroleum sulfonate), 3% (w/w) isobutanol and equal volumes of aqueous and dodecane oil phases was studied by scanning electron microscopy. The microstructure of these emulsions together with that of the mutually equilibrated oil and aqueous phases was investigated by electron spin resonance (ESR) technique. Extensive physical property data for the emulsion system and for the equilibrated phases were measured. The phase inversion of emulsions from O/W type at low salinities to W/O type at high salinities was confirmed by ESR, viscosity and electrical conductivity measurements. With increasing salt concentration, the macroemulsion passed through a series of structural changes as revealed by the electron microscopy results. A detailed analysis of viscosity and electrical conductivity of the emulsions is presented. The anomalous behavior of the emulsion at optimal salinity is highlighted. A discussion to correlate the structure, stability and type of emulsions with physical property behavior as a function of electrolyte concentration is included.     

Co-pyrolysis of sugarcane bagasse with petroleum residue. Part II. Product yields and properties

The main objective of the present work was to study the pyrolysis under vacuum of sugarcane bagasse combined with petroleum residue (PR), in terms of yields and properties of the products obtained. Important synergetic effects were observed during the co-pyrolysis in a fixed bed reactor leading to an increase in charcoal yield. Maximum charcoal and minimum oil yields were obtained with 15 wt% of PR mixed with bagasse. At this concentration, sugarcane bagasse charcoal is almost completely covered with PR-derived pyrolytic carbon. At concentrations higher than 15 wt%, hydrocarbon vapours interacted less with the bagasse charcoal. Consequently, an appreciable increase in oil yield was observed. The oils obtained are complex emulsions, which consist of oxygenated compounds originating from bagasse, hydrocarbons originating from PR and water. Oils obtained from feedstock with concentrations up to 15 wt% PR are stable emulsions consisting of PR-derived products in bagasse-derived oil. The oil obtained from the 30 wt% PR-bagasse blend is an unstable emulsion. However, the emulsion obtained at 50 wt% PR is again stable. In this emulsion, the PR-derived oil constitutes a continuous phase. This emulsion exhibits a carbon Conradson residue value (9 wt%) similar to that of PR-derived oil. A detailed characterization of the gas, oil and charcoal co-pyrolysis products is presented.     

Destabilization‐Enhanced Centrifugation of Metalworking Oil‐in‐Water Emulsions: Effect of Demulsifying Agents

The effect of a commercial flocculant (Alpacon® WS009) and two coagulant salts (CaCl₂ and AlCl₃) on the stability of metalworking oil‐in‐water (O/W) emulsions was examined. Two O/W emulsions were tested: a fresh emulsion, prepared in the laboratory from a commercial concentrate, and a waste metalworking emulsion, provided by a local waste management company, with initial oil concentrations of 32900 and 16900 mg/L, respectively. The emulsion stability was studied at different demulsifier concentrations, temperatures and pH through centrifugation tests, zeta potential and multiple light scattering measurements. Emulsion breakdown is explained by electrostatic repulsion of oil droplets and steric interactions. The former was observed for the laboratory emulsion, while the latter was observed for the waste emulsion. Aluminum chloride was the only effective agent for demulsifying both emulsions.     

Physico-chemical properties of heavy crude oil-in-water emulsions stabilized by mixtures of ionic and non-ionic ethoxylated nonylphenol surfactants and medium chain alcohols

This work describes the formulation and evaluation of concentrated, heavy oil-in-water emulsions stabilized by mixtures of ethoxylated surfactants and normal alcohols. The rheology, stability and droplet size of these emulsions were investigated as functions of the emulsification process parameters. The parameters investigated for this study include emulsifier agent composition, presence of additives, pH and salinity of the continuous aqueous phase, emulsification temperature, oil content and emulsion aging. The produced emulsions had viscosities ranging from 30 to 150 mPa s and represent a 30-fold reduction of the crude oil viscosity. Sauter mean diameters of the droplets ranged from 10 to 50 μm. The emulsions were produced by mixing the oil with an aqueous solution containing medium normal-chain alcohols and small quantities of a mixture of ethoxylated nonylphenol and ethoxylated amine surfactants. The presence of these alcohols led to a sharp decrease in the droplet size of the emulsion. This size decrease had a direct impact on the emulsions’ stability and apparent viscosity. The rheological parameters of the aged emulsions were also essentially constant over a 42-day period.     

Experimental and modeling approach to study separation of water in crude oil emulsion under non-uniform electrical field

In many ways, the use of high electrostatic fields in the separation of water-in-oil emulsions is a mature technology, with most developments arising from attempts to improve the process of crude oils, in terms of the separation of water, salt or other hydrophilic impurities. In this way, different mechanisms have been proposed until now and several parameters have been studied to estimate the level of separation. In this work, after a review of the process and its application, new results are presented for AC currents under non-uniform electrical fields (dielectrophoresis) on the water-in-crude oil emulsion. Then the effects of voltage, temperature, volume fraction and API are studied on degree of separation. Finally, a correlation is presented among these parameters by an experimental model.     

Characterization of a double emulsion system (oil-in-water-in-oil emulsion) with low solid fats: Microstructure

A double emulsion system [oil-in-water-in-oil (O/W/O)] with 16.3% (w/w) water and 83% (w/w) oil was prepared and stabilized using a novel method of mixing two oil-in-water (O/W) emulsions together. The first emulsion consisted of 85% (w/w) liquid canola oil, 14.4%(w/w) water, 0.5% (w/w) sodium caseinate, and 0.1% (w/w) lecithin and the second emulsion contained 73% (w/w) canola oil, 8% (w/w) palm-cotton stearin (50∶50), 0.2% (w/w) lecithin, 18.2% (w/w) water, and 0.6% (w/w) sodium caseinate. Mixing the two emulsions (50∶50) by weight produced a product with 79% (w/w) liquid canola oil and 4% (w/w) palm-cotton stearin. The two O/W emulsions were prepared separately at 50°C, mixed together at 45°C for 2–5 min, and then supercooled in a −5°C ice/salt bath while mixing at low shear rates (2,000–3,000 rpm). Under supercooling conditions the fat globules in the second emulsion (containing liquid oil and stearin) began to break down as a result of fat crystal growth and shearing action and release plastic fat. During this stage, the continuous aqueous phase underwent a phase transition and the emulsion viscosity dropped from 37,000–50,000 to 250 cP. The released plastic fat continued to harden as the temperature dropped and stabilized the first O/W emulsion (containing only liquid oil). The low shear rate mixing was stopped when the temperature dropped below 15°C and before the O/W/O emulsion hardens. Microstructural analysis of the first emulsion before and after supercooling showed essentially intact fat globules. The microstructure of the second emulsion before supercooling showed the same intact globules as the first emulsion, but after supercooling, an amorphous mass with only a few intact globules was seen. By mixing the two emulsions together and supercooling, a stable O/W/O emulsion was formed with plastic fat as the continuous phase and the first O/W emulsion as the dispersed phase.     

Emulsification characteristics of three- and two-phase emulsions prepared by the ultrasonic emulsification method

Diesel engines exhausting gaseous emission and particulate matter have long been regarded as one of the major air pollution sources, particularly in metropolitan areas, and have been a source of serious public concern for a long time. The emulsification method is one of the potentially effective techniques to reduce emission pollution from diesel engines. Ultrasonic waves are a kind of sound waves with a frequency larger than 20 kHz, and they cannot be detected by the human ear. The phenomena of cavitation and hot spots produced by the rather violent action of ultrasonic waves can cause rapid chemical and physical reactions. This allows immiscible liquids to be well stirred with each other by means of ultrasonics. An ultrasonically vibrating machine that provides ultrasonic waves of a 40-kHz frequency was employed to prepare two- and three- phase emulsions in this experimental study. The fuel properties and the emulsion stability of the diesel emulsions were measured and analyzed. Experimental results show that the ultrasonic emulsification method successfully prepared two- and three-phase emulsions with tiny dispersed-phase droplets that are very evenly distributed in the outer oil or water phase. The ultrasonic processing time, quantity and HLB of the emulsifying agent were noted to have determinative influences on the formation of the emulsion and the fuel properties. A longer ultrasonic processing time caused less un-emulsified diesel fuel, smaller sizes and a more even distribution of dispersed-phase droplets in the outer oil phase and larger emulsion viscosity. However, a longer ultrasonic processing time also produced a larger temperature rise in the emulsion, leading to the deterioration of the emulsion stability. The O/W emulsion was found to have the lowest percentage of separation and thus the highest emulsion stability among the O/W/O, O/W and W/O emulsions. In addition, in comparison with the W/O emulsion, the O/W emulsion was shown to have a smaller size and a more even distribution of the dispersed-phase droplets. It also had a lesser rise in emulsion temperature when the ultrasonic processing time increased. The control of the ultrasonic processing time is important to successfully prepare the three-phase O/W/O emulsion. Too long a vibration time at the second-stage of emulsification is shown to cause the dispersed-phase pellets to contract and congregate with the inner-phase droplets. The three-phase emulsion structure then finally disappears and transforms into a two-phase emulsion. The addition of 2% by volume of the emulsifier mixture of Span80 and Tween80 with a HLB = 8, as suggested by this study for the preparation of stable two- and three-phase emulsions, were observed to have the lowest percentage of separation of the W/O and O/W/O emulsions. For preparing a stable O/W emulsion, the proportion of the emulsifier could be as low as 1.5% by volume. The percentage of separation of the O/W/O emulsion was lower and less influenced by the change in emulsion temperature than was the W/O emulsion with the same water content. However, the O/W/O emulsion was found to have a larger viscosity and a more significant variation of its viscosity, depending on the ultrasonic processing time, than the W/O emulsion.     

高频脉冲电场作用下乳状液液滴动力学模型

基于乳状液中液滴在电场中的受力情况的分析,建立了W/O乳状液中液滴振荡固有频率公式,从理论角度分析和解释了高频脉冲电场对W/O乳状液的破乳机理,从力学的角度分析了最佳频率存在的理论基础,并推导出了最佳频率的计算公式。该固有频率与液滴尺寸、界面张力、黏度、温度、密度等有关。为了验证最佳频率公式的可靠性,用正辛烷乳状液进行了室内实验。实验结果表明,理论最佳频率公式的预测结果与实验测得的最佳频率结果吻合,经修正后与白油实验结果也非常接近。     

A novel method for preparing oil-in-water-in-oil type multiple emulsions using organophilic montmorillonite clay mineral

A stable formula using oil-in-water-in-oil (O/W/O) type multiple emulsions was investigated. The components consisted of hydrophilic nonionic surfactant (HCO-60), organophilic montmorillonite, and lipophilic nonionic surfactant (DIS-14). O/W/O emulsions were prepared by a double-step procedure in which an O/W emulsion was prepared in the first step, and then the O/W emulsion was “re-emulsified” in an oil phase with organophilic montmorillonite. The diameter of the innermost oil droplets decreased with increasing HCO-60 content (0.1–3%), while the viscosity showed a maximum at 1% of HCO-60, indicating that the yiel of re-emulsification is highest at this condition. Viscosity of the O/W/O emulsion increased with increasing organophilic montmorillonite and DIS-14. According to the results of a phase ratio study, viscosity and stability of the O/W/O emulsion decreased at high weight fraction of inner oil phase (0.4–0.5), indicating that the excess amount of inner oil phase is absorbed by the outer oil phase. These results revealed that the weight fraction of inner oil phase should be kept below 0.3 for a stable O/W/O emulsion. A similar study on the weight fraction of O/W phase [фO/W)/O] suggested that the O/W/O emulsion is stable at ϕ(O/W)/O=0.65–0.70.     

Stability of vitamin A in oil-in-water-in-oil-type multiple emulsions

The stabilityof vitamin A was studied in thee different emulsions: oil-in-water (O/W), water-in-oil (W/O), and oil-in-water-in-oil (O/W/O). The stability of retinol (vitamin A alcohol) in the O/W/O emulsion was the highest among the thee types of emulsions; remaining percentages at 50°C after 4 wk in the O/W/O, W/O, and O/W emulsions were 56.9, 45.7, and 32.3, respectively. With increasing peroxide value of O/W and W/O emulsifiers, the remaining percentage of vitamin A palmitate and retinol in the emulsions decreased significantly, indicating that peroxides in the formulae accelerate the decomposition of vitamin A. Organophilic clay mineral (an oil gelling agent and a W/O emulsifier) also affected the stability of retinol; synthesized saponite was better than naturally occurring bentonite for retinol stability. The stability of retinol in the O/W/O emulsion increased with increasing inner oil phase ratio (φ_i), whereas in O/W it was unaffected by φ_i. Encapsulation percent of retinol in the O/W/O emulsion, the ratio of retinol in the inner oil phase to the total amount in the emulsion, increased with increasing φ_i. The remaining percent of retinol in the O/W/O emulsion was in excellent agreement with encapsulation percent, suggesting that retinol in the inner oil phase is more stable than that in the outer oil phase. Addition of antioxidants (tert-butylhydroxytoluene, sodium ascorbate, and EDTA) to the O/W/O emulsion improved the stability of retinol up to 77.1% at 50°C after 4 wk. We conclude that the O/W/O emulsion is a useful formula to stabilize vitamin A.     

玉米油W1/O/W2型多重乳状液稳定性的研究

高脂食品严重危害着人类健康,这引起人们对低脂食品的的不断追求,因此脂肪替代品的开发越来越受到人们重视。本试验以玉米油和生物高聚物为主要原料通过两步乳化法制备W1/O/W2多重乳状液作为脂肪替代品(FS),以离心稳定性为衡量标准,用显微镜直接观察,探讨了初复乳乳化工艺、各相相对体积比对玉米油W1/O/W2型多重乳状液体系稳定性的影响。结果表明:1.影响玉米油多重乳状液稳定性的主要因素有:复乳的乳化工艺,内水相与油相体积之比等。2.两步乳化工艺中第二步乳化工艺对复乳稳定性影响较大,其规律是随着乳化强度的提高,粒径减小,稳定性呈上升趋势,适宜的乳化条件为7200 r.min.1,13 min,而第一步乳化工艺对复乳稳定性几乎没有影响。3.内水相与油相、初乳与外水相均是影响复乳稳定性的主要因素,前者主要是依靠改变初乳黏度来影响复乳稳定性,后者主要是乳滴间范德华力与电排斥力共同作用的结果,适宜的体积比分别为1:4和1:1。     

Effects of Curcumin on the Oxidative Stability of Oils Depending on Type of Matrix,Photosensitizers, and Temperature

The photosensitizing activity of curcumin was tested in corn oil and oil‐in‐water (O/W) emulsion systems under visible light irradiation. In addition, the antioxidative/prooxidative properties of curcumin were evaluated in corn oil at 100 °C and in O/W emulsion at room temperature under riboflavin photosensitization or at 60 °C in the dark. Curcumin acted as a photosensitizer in corn oil and O/W emulsions . The oxidative stability of corn oil samples containing curcumin (0–5.0 mmol/kg oil) were not significantly different (p > 0.05) at 100 °C, implying curcumin did not act as an antioxidant nor a prooxidant in corn oil. However, curcumin inhibited lipid oxidation in O/W emulsions under riboflavin photosensitization at room temperature and 60 °C in the dark. The photosensitization and antioxidant abilities of curcumin were greatly influenced by matrix types and presence of riboflavin. Therefore, antioxidative or prooxidative characteristics of curcumin should be evaluated considering matrix type including bulk oil or O/W emulsions and presence of visible light irradiation.     

Effects of emulsification variables on fuel properties of two- and three-phase biodiesel emulsions

Biodiesel has attractive fuel properties such as excellent biodegradability and lubricity, almost no emissions of sulfur oxides, PAH and n-PAH, reduced CO₂, PM and CO emission, superior combustion efficiency, etc. However, burning of biodiesel generally produces higher levels of NO_x emissions, primarily due to its high oxygen content. In this study, the emulsification technology has been considered to reduce the NO_x emission level of fossil fuel. Biodiesel, produced by means of transesterification reaction accompanied with a peroxidation process, was emulsified to form two-phase W/O and three-phase O/W/O emulsions. The effects of the emulsification variables such as hydrophilic lipophilic balance (HLB), and water content on the fuel properties and emulsion characteristics of W/O and O/W/O emulsions were investigated in this study. The experimental results show that the surfactant mixture with HLB = 13 produced the highest emulsification stability while HLB = 6 produced the lowest emulsification stability and the most significant extent of water–oil separation among the various HLB values for O/W/O biodiesel emulsion. The kinematic viscosity, specific gravity and carbon residual of the biodiesel emulsions were larger than those of the neat biodiesel. In addition, the W/O biodiesel emulsion was found to have a smaller mean droplet size, lower volumetric fraction of the dispersed phase than the O/W/O biodiesel emulsion, and the highest heating value among the test fuels, if the water content is deducted from the calculation of the heating value.     

低压脉冲电场对高浓度O/W型乳化液破乳特性的影响

为实现高含油浓度O/W型乳化液的电场破乳预分水,借鉴电絮凝技术的工作原理自行设计了静态序批式电场破乳预分水实验装置。在对乳化液理化特性进行量化表征以确保其稳定性的基础上,以预分水率为主要评价指标,系统实验研究了电场形式、峰值电压、脉冲频率、占空比及含水率对O/W型乳化液静态破乳预分水特性的影响。结果发现,脉冲直流方波电场下乳化液的破乳效果比直流电场较好;含水率降低使乳化液的破乳程度减弱;峰值电压、脉冲频率和占空比都存在一个最优值。当施加脉冲直流方波电场、电压幅值为40V、脉冲频率为2kHz、占空比为0.5、加电时间为30min时,含水率90%乳化液的预分水率达87.18%。基于实验过程中的现象推测,高含油浓度O/W乳化液的破乳预分水机理包括双电子层作用和类似电絮凝作用。     

Membrane Recovery in Liquid Membrane Separation Processes

Abstract

The use of conventional electrostatic coalescers with bare metal electrodes for the separation of rich water-in-oil emulsions often causes the formation of a sponge-like emulsion. This effect was eliminated by the use of insulated electrodes in a coalescer that allow the application of high electric fields at the oil/water interface, resulting in a clean separation of oil from water.